1. Field of the Invention
The present invention relates in general to vehicle bodies having rod-like protrusions on the exterior surface thereof and more particularly to improvements in such rod-like protrusions which reduce wind noise when the vehicle is travelling at a high speed.
2. Description of the Prior Art
A vehicle body has on the exterior surface thereof various rod-like protrusions such as an antenna, roof carrier, outside mirrors, etc. Such protrusions are one of the causes for automotive wind noise. For example, wind noise due to an antenna results from resonance occurring when a Karman vortex sheet is shed in the wake of the antenna and its vortex shedding frequency is equal or near to the natural vibration frequency of the antenna. In this connection, it is known that the vortex shedding frequency is directly proportional to the velocity of air flowing past the antenna and inversely proportional to the diameter of the antenna. Accordingly, during the running of a vehicle having a rod-like protrusion, a vortex of a Karman vortex sheet extending continuously lengthwise of the rod-like protrusion and in the wake of same is created depending upon the running speed of the vehicle, which causes wind noise of an intensity proportional to the vortex shedding frequency.